Effect of temperature on development and growth potential of axillary buds in roses

The effect of temperature during axillary bud formation on axillary bud development and subsequent shoot growth was investigated. Growth potential of the axillary buds was studied either in situ, by pruning the parent shoot above the bud, or in isolation, by grafting the bud or by culturing the bud in vitro. Although rate of leaf initiation increased with increasing temperature, the number of leaves and leaf primordia in the bud at the time of release from inhibition decreased slightly with increasing temperature. Time until bud break decreased with increasing temperature, as did the total growth period until harvest. The total number of leaves preceding the flower decreased with increasing temperature, while no difference in leaf number was found between shoots grown from buds in situ and shoots from buds in isolation. Shoot size at harvest (sepals reflexing) decreased slightly with increasing pre-treatment temperature, but effects were larger for isolated buds than for buds attached to the parent shoot. The pith to shoot diameter ratio was not affected by temperature and the number of pith cells in cross section decreased only slightly with increasing temperature.